Unidentified Vibration M1008

[frontiersman]

I have an 84 M1008. Runs perfect, drives really good, steering is tight, transmission and transfer case work without problems. This truck came auction at Camp Shelby. I have had to do the usual things to get it road worthy and running correct. The issue I have now is while on the road there is an intermittent vibration that I think is towards the front of the truck. I cannot feel the vibration but can hear it. Turning either way has no effect. I suspected bad front shaft joints but they have zero play. Hubs are unlocked. Have tried running in 4 low, 4 high, then unlocking the hubs. I have studied the TM'S but cannot identify the problem. Any suggestions?

 

[dmetalmiki]

Prop shaft?....Engine mounts?...and of course flywheel runout.> (fluid flywheel torque converter) As another thought have you actually looked at the wheel bearings?. Hope you sort it..Let us know findings, and rectification.

 

[frontiersman]

Prop shaft?....Engine mounts?...and of course flywheel runout.> (fluid flywheel torque converter) As another thought have you actually looked at the wheel bearings?. Hope you sort it..Let us know findings, and rectification.

Rear drive shaft does not appear to have been bent, nor does the front shaft. Noise does not occur while sitting still, or revving the engine. No noticeable engine movement while in gear, holding brakes, and revved. I really don't know where to start. One thought is a tire out of balance, or a front steering piece that has play while driving, but the strange part it doesn't matter which way you turn while driving, the noise doesn't change.

 

[frontiersman]

Have not looked at the wheel bearings.

 

[dependable]

Take a look at the harmonic balancer too.

 

[frontiersman]

Take a look at the harmonic balancer too.

I know the harmonic balancer needs replacing, the rubber is cracked. However, would a bad balancer not make the noise in sync with engine rpm?

 

[2deuce]

My M1009 has a similar problem with vibration, but mine comes on strong on acceleration. Mine also acts like yours when reving in park. The engine mounts hold the engine with the brake on, but it shakes good at 35 and accelerating but goes away above 50. Any similar to that with your M1008? If your power steering is low you can get a growling sound and some light vibration along with it.

 

[frontiersman]

Just redid the power steering system with a new pump, belt, and on hose that was leaking. I am about convinced the rear drive shaft is the problem. On inspection I cannot see where it has been dented or bent, and there are weights welded on. I just do not know how to test this theory without taking the shaft out and to a shop.

 

[2deuce]

Don't concern yourself with the weights, that is how it was balanced. If you don't have time to take it to be tested. Take it off and run the truck with the front wheels for a test.

 

[jpg]

If you can't feel it, perhaps it's just a harmonic causing a rattle? My wife's VW got recalled due to a problem like that. The solution was to put foam rubber in between 2 adjacent body parts that normally touch. Harmonics would cause the 2 parts to "clap" against each other when the car vibrated just right. On another vehicle, I had this happen once where the jack was the culprit. It was loose in its mount and rattled when the vibration was just right. I tightened it in its mount, and the noise was fixed.

 

[dependable]

About the vibration not being in sync with RPM, don't know, but one of my 1008s developed new vibration & I knew the balancer was worn, so I replaced it and the vibration went away. One guy I know had a crankshaft break because he did not get around replacing a balancer he knew was bad. He posted about it here a while ago.

That said, I would suspect the tires also. Have had a few trucks with low mileage but old tires come from GL that proved to have cord failure. Have also had one blister when hot, so it only vibrated after driving a while, and the blister would go away once it had cooled.

 

[frontiersman]

Ok, this is what I am going to do to "test" my rear drive shaft theory. I am going to put the rear of the truck on jack stands, scotch the front wheels, and "drive" it enough to shift through the gears. Will have a buddy watching from the side for any noticeable weird movement in shaft, and listen for the noise. If it's there, then bad shaft. If not, then I will pull the shaft and use 4h to run down the road to listen for noise. If noise is gone, then it has to be shaft, if not then I have no clue. Either way a new harmonic balancer is going on engine this weekend.

 

[welpro222]

Every new 6.2 diesel truck I've bought, first thing it gets is a new fuel filters and a new Powerbond balancer. Most all OEM and aftermarket ones are made in China, Powerbond is made in Australia. I have compared the Powerbond side by side with others and the PB seems like it is far better quality.

 

[frontiersman]

Think I have found the problem. At lower rpms you can see the drive shaft "wiggling" but can't see it at higher rpms. Truck would not shift out of 1st while on blocks I'm guessing due to lack of driving pressure. Never heard the vibration either, but logic tells me that driving on the road plus the wiggle in drive shaft will manifest as the the intermittent vibration? Anyone in or near west AL have a good used shaft for sale?

 

[frontiersman]

Every new 6.2 diesel truck I've bought, first thing it gets is a new fuel filters and a new Powerbond balancer. Most all OEM and aftermarket ones are made in China, Powerbond is made in Australia. I have compared the Powerbond side by side with others and the PB seems like it is far better quality.

O'Reilly lists 2 for a 1984 K30 with the 6.2. Attached is a pic if one they have on the shelf.